Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
Langmuir. 2011 Dec 20;27(24):15074-82. doi: 10.1021/la203101y. Epub 2011 Nov 14.
Electroformed giant unilamellar vesicles containing liquid-ordered Lo domains are important tools for the modeling of the physicochemical properties and biological functions of lipid rafts. Lo domains are usually imaged using fluorescence microscopy of differentially phase-partionioning membrane-embedded probes. Recently, it has been shown that these probes also have a photosensitizing effect that leads to lipid chemical modification during the fluorescence microscopy experiments. Moreover, the lipid reaction products are able as such to promote Lo microdomain formation, leading to potential artifacts. We show here that this photoinduced effect can also purposely be used as a new approach to study Lo microdomain formation in giant unilamellar vesicles. Photosensitized lipid modification can promote Lo microdomain appearance and growth uniformly and on a faster time scale, thereby yielding new information on such processes. For instance, in egg phosphatidylcholine/egg sphingomyelin/cholesterol 50:30:20 (mol/mol) giant unilamellar vesicles, photoinduced Lo microdomain formation appears to occur by the rarely observed spinodal decomposition process rather than by the common nucleation process usually observed for Lo domain formation in bilayers. Moreover, temperature and the presence of the ganglioside GM1 have a profound effect on the morphological outcome of the photoinduced phase separation, eventually leading to features such as bicontinuous phases, phase percolation inversions, and patterns evoking double phase separations. GM1 also has the effect of destabilizing Lo microdomains. These properties may have consequences for Lo nanodomains stability and therefore for raft dynamics in biomembranes. Our data show that photoinduced Lo microdomains can be used to obtain new data on fast raft-mimicking processes in giant unilamellar vesicles.
电铸的含有液晶有序 Lo 区的巨大单层囊泡是模拟脂质筏的物理化学性质和生物功能的重要工具。Lo 区通常使用荧光显微镜对差异相分区的膜嵌入探针进行成像。最近，已经表明这些探针还具有光致敏作用，在荧光显微镜实验过程中导致脂质化学修饰。此外，脂质反应产物本身能够促进 Lo 微区形成，导致潜在的假象。我们在这里表明，这种光诱导效应也可以被有意用作研究巨大单层囊泡中 Lo 微区形成的新方法。光致敏脂质修饰可以均匀且更快地促进 Lo 微区的出现和生长，从而提供有关这些过程的新信息。例如，在鸡蛋磷脂酰胆碱/鸡蛋神经鞘磷脂/胆固醇 50:30:20（摩尔/摩尔）巨大单层囊泡中，光诱导 Lo 微区形成似乎通过很少观察到的旋节分解过程发生，而不是通过通常观察到的双层中 Lo 域形成的成核过程。此外，温度和神经节苷脂 GM1 的存在对光诱导相分离的形态结果有深远的影响，最终导致双连续相、相渗透反转和类似双相分离的图案等特征。GM1 还具有破坏 Lo 微区的作用。这些性质可能对 Lo 纳米区的稳定性产生影响，从而对生物膜中的筏动力学产生影响。我们的数据表明，光诱导的 Lo 微区可用于获得有关巨大单层囊泡中快速筏模拟过程的新数据。
